Erosion and wear resistant sonoelectrochemical probe

ABSTRACT

The present invention, in one set of embodiments, provides methods and systems for integrating conducting diamond electrodes into a high power acoustic resonator. More specifically, but not by way of limitation, in certain embodiments of the present invention, diamond electrodes may be integrated into a high power acoustic resonator to provide a robust sensing device that may provide for acoustic cleaning of the electrodes and increasing the rate of mass transport to the diamond electrodes. The diamond electrodes may be used as working, reference or counter electrodes or a combination of two or more of such electrodes. In certain aspects, the high power acoustic resonator may include an acoustic horn for focusing acoustic energy and the diamond electrodes may be coupled with the acoustic horn.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 12/719,226 filed Mar. 8, 2010; which is a divisionalapplication of U.S. patent application Ser. No. 11/499,332 filed Aug. 4,2006, now U.S. Pat. No. 7,710,000 issued May 4, 2010; both of theseapplications are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

Combining high power ultrasound and electrochemical analysis functionsand properties has most often previously been achieved by configuring ahigh power acoustic resonator and separate electrode system in a face-ongeometry. In such an arrangement, the spacing between the electrode andacoustic resonator can be varied to vary the effect of the separatedacoustic and electrode systems. However, it should be noted, that thespacing between the acoustic resonator and the electrode system in theface-on geometry will result in a decrease in the electrode cleaningcapabilities of the acoustic resonator and the mass transfer rateassociated with the electrode when operated contemporaneously with theacoustic resonator. Furthermore, investigations with regard toperformance of such face-on configurations identified the existence ofwear and erosion issues associated with the systems

In another arrangement configured to provide for combined ultrasound andelectrochemical analysis functions and properties, an acoustic horn of ahigh power acoustic resonator has itself been used as an electrode. Inthese configurations, the acoustic horn itself is used as the workingelectrode in an electrochemical circuit. Reisse et al. in an articleentitled “SONOELECTROCHEMISTRY IN AQUEOUS ELECTROLYTE: A NEW TYPE OFSONOELECTROREACTOR ,” Electrochim. Acta, 39, 37-39 (1994), discloseusing a titanium ultrasonic horn as a working electrode to provide fordepositing copper from a solution of copper sulphate in the presence ofhigh power ultrasound at a frequency of 20 kHz. Durant et al. describeusing a titanium horn as the working electrode to study the effects ofhigh power ultrasound on the electrochemical reduction of benzaldehydeand benzoquinone. (Durant, A., François, H., Reisse, J. and Kirsch-deMesmaeker, A., “SONOELECTROCHEMISTRY: THE EFFECTS OF ULTRASOUND ONORGANIC ELECTROCHEMICAL REDUCTION ,” Electrochim. Acta, 41, 277-284(1996).

Other arrangements provide for attaching the electrode to an acoustichorn. Such an arrangement may be termed a sonotrode and such a device isavailable commercially from Windsor Scientific. The Windsor Scientificsonotrode consists of a glassy carbon disk electrode set in the end of aquartz rod, wherein the quartz rod is screwed into the end of anultrasonic horn. Although the sonotrode is a combined system with theacoustic resonator and electrode combined, the electrode is stilldisposed distally from the acoustic horn; so as with the face-ongeometry, the separation will result in a decrease in the electrodecleaning capabilities of the acoustic resonator and the mass transferrate associated with the electrode when operated contemporaneously withthe acoustic resonator. Further, the Windsor Scientific sonotrode doesnot provide a rugged and wear/erosion resistant design and may not becapable of operating at high acoustic powers and/or may experiencedegradation of the glassy carbon disk electrode under acousticfunctions. In another sonotrode-type device, Simm et al. “SONICALLYASSISTED ELECTROANALYTICAL DETECTION OF ULTRATRACE ARSENIC ,” Anal.Chem., 76, 5051-5055 (2004), an electrode may be attached to a smallpermanent magnet that may be made to vibrate by passing current throughan adjacent electric coil.

In a further acoustic resonator and electrode arrangement, modifying theidea of using the acoustic horn as the electrode, a platinum electrodeis disclosed that is bonded into a hole drilled in the titanium tip ofan acoustic horn using an adhesive. (Compton et al., “ELECTRODEPROCESSES AT THE SURFACE OF SONOTRODES ,” Electrochim. Acta, 41, 315-320(1996)). In such an arrangement, as with arrangements wherein theacoustic horn acts as an electrode, the distance between the electrodeand the acoustic horn does not become an issue. In the electro-acousticsystem disclosed by Compton, electrical connections to the platinumelectrode are provided by wire connections passing through the side ofthe acoustic horn to the platinum electrode. While the referenceprovides a sonotrode that effectively addresses issues regardingseparation of the acoustic resonator and the electrode it does notaddress using acoustic energy to clean the electrode or provide foreffectively configuring the acoustic resonator and electrode system forcombined operation. Furthermore, the reference does not disclose asonotrode that may be suited for remote operation, operation in harshenvironments—including high temperatures or pressures—or that can beeffectively used repeatedly at high acoustic energy levels.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention relate to integrating an electrodesystem with a high power acoustic resonator. More specifically, but notby way of limitation, embodiments of the present invention provide forintegrating a diamond electrode with the high power acoustic resonatorto provide a sonoelectrochemical interface that is erosion and wearresistant that may be used in fouling and harsh environments and iscapable of remote operation. Additionally, in certain embodiments of thepresent invention, by integrating the electrode system into an acoustichorn of the acoustic resonator the system may provide for effectivecleaning of the electrode and effective operation of thesonoelectrochemical interface at high acoustic energies.

In one embodiment, an erosion and wear resistant sonoelectrochemicalprobe configured for high power ultrasonic operation is providedcomprising a high power acoustic resonator with an acoustic body and atransducer coupled to the base of the acoustic body, a diamond electrodecoupled with a tip of the acoustic body and an electrically conductingelement coupled with the diamond electrode. In one aspect of theinvention, the diamond electrode may be a diamond microelectrode array.In certain aspects, the electrically conducting element may be disposedwithin the acoustic body so that it passes from the tip of the acousticbody and through the base of the acoustic body. Disposing theelectrically conducting element inside the acoustic body may provide fora sonoelectrochemical probe that may be used in extreme conditionsand/or for effective operation of the acoustic resonator at high powerswith the combined electrode system.

The diamond electrode may comprise a boron-doped diamond. In certainaspects, the boron-doped diamond electrode may be configured so thatthere is a central disc of boron-doped diamond surrounded by aconcentric ring of non-conducting diamond, wherein the concentric ringof electrically non-conducting diamond provides for the insulation ofthe central disc of the boron-doped diamond from the acoustic body. Infurther embodiments of the present invention, the diamond electrode maycomprise a macroscopic and/or a microscopic array formed fromboron-doped diamond regions and electrically non-conducting diamondregions. In certain aspects, the boron-doped diamond regions andelectrically non-conducting diamond regions may be arranged inconcentric rings around a central disc of boron-doped diamond. In thearray and ring-type configurations of the non-conducting andelectrically conducting diamond, the individual electrodes of thesonoelectrochemical probe formed by the electrically isolated regions ofthe electrically conducting diamond may be configured to provideworking, counter and reference electrodes. In such configurations, thesonoelectrochemical probe may comprise a complete and robust, integratedsystem for performing sonoelectrochemistry measurements.

In an embodiment of the present invention, the rugged and wear resistantsonoelectrochemical probe may be contacted with a substance or thesubstance may be made to contact the sonoelectrochemical probe, a secondelectrode may also be contacted with the substance, the high poweracoustic resonator may be used to generate acoustic energy andelectrical properties of an electrical current flowing betweensonoelectrochemical probe and the second electrode may be measured.Further, a third electrode may also be contacted with the substance. Thesecond electrode may be coupled with the sonoelectrochemical probe toprovide an integrated system for taking sonoelectrochemicalmeasurements. Yet further, the third electrode may be coupled with thesonoelectrochemical probe and the second electrode to provide a threeelectrode integrated system for taking sonoelectrochemical measurementusing the working, reference and counter electrode system well know tothose skilled in the art. In other aspects, multiple electrodes may beformed on the active face of the sonoelectrochemical probe by thecreation of regions of electrically conducting diamond on the electrodesurface of the sonoelectrochemical probe, electrically insulated fromeach other. In certain aspects, these electrically isolated regions maybe areas of electrically conducting diamond surrounded by non-conductingdiamond, and these multiple electrodes may be used as working andreference electrodes and/or counter electrodes. In certain aspects, thehigh power acoustic resonator may be used to generate acoustic energy toclean the sonoelectrochemical probe and/or to mix the substance orsubstances in contact with the sonoelectrochemical probe.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating various embodiments of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures, similar components and/or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a schematic type illustration of a high power acousticresonator that may be used in an embodiment of the present invention;

FIG. 2 is a schematic-type diagram illustrating a high power acousticresonator with an integrated electrically conducting diamond electrode,in accordance with an embodiment of the present invention;

FIG. 3 is a schematic-type diagram illustrating a high power acousticresonator with an integrated diamond electrode comprising a plurality ofconducting regions separated by non-conducting regions that may be usedas reference or counter electrodes and working electrodes, in accordancewith an embodiment of the present invention; and

FIG. 4 is a schematic-type diagram illustrating a high power acousticresonator with an integrated diamond electrode array, in accordance withan embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The ensuing description provides preferred exemplary embodiment(s) only,and is not intended to limit the scope, applicability or configurationof the invention. Rather, the ensuing description of the preferredexemplary embodiment(s) will provide those skilled in the art with anenabling description for implementing a preferred exemplary embodimentof the invention. It being understood that various changes may be madein the function and arrangement of elements without departing from thespirit and scope of the invention as set forth in the appended claims.

Specific details are given in the following description to provide athorough understanding of the embodiments. However, it will beunderstood by one of ordinary skill in the art that the embodimentsmaybe practiced without these specific details. For example, circuitsmay be shown in block diagrams in order not to obscure the embodimentsin unnecessary detail. In other instances, well-known circuits,processes, algorithms, structures, and techniques may be shown withoutunnecessary detail in order to avoid obscuring the embodiments.

Also, it is noted that the embodiments may be described as a processwhich is depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be re-arranged. A process is terminated when itsoperations are completed, but could have additional steps not includedin the figure. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination corresponds to a return of the functionto the calling function or the main function.

Interest in the combination of high power ultrasound and electrochemicalanalysis has developed based upon an understanding of the advantages ofusing high power ultrasound when making electrochemical measurements andthe term sonoelectrochemistry has been coined to describe the union ofhigh power ultrasound and electrochemical measurements. In particular,two advantages have been observed in the use of high power ultrasoundwith electrochemical measurements.

With regard to the first advantage, it has been found that the use ofultrasound significantly increases the rates of mass transport to andfrom an electrode and, thus, causes an increase in the measuredelectrical current. This increase is caused by an increase in the flowof electrolyte solution past the working electrode, which is caused byacoustic cavitation and/or acoustic streaming. This gives rise to whatis essentially hydrodynamic control of mass transport.

In a sonoelectrochemical system comprising an electrode-typeelectrochemical system and an acoustic system, the steady state limitingcurrent (I_(lim)) may be described by equation (1):

$\begin{matrix}{I_{{li}\; m} = \frac{nFACD}{\delta}} & \lbrack 1\rbrack\end{matrix}$where n is the number of electrons involved in the electrochemicalreaction, F is the Faraday constant, A is the area of the electrode, Cis the concentration of the electroactive species in bulk solution, D isthe diffusion coefficient of the electroactive species in the solutionand 6 is the thickness of the stagnant diffusion layer between theelectrode and the bulk electrolyte solution. In experiments, values of δof one μm have been reported, which are considerably smaller than valuesachieved under quiescent conditions. From experimentation and analysis,some researchers have found that equation [1] may be expressed as:I _(lim) =nFACm _(i)  [2]where m_(i) is the average mass transport coefficient. In theseexperiments, the researchers commented that mass transport ratesachieved by the application of high power ultrasound can be 100-1000times greater than with other hydrodynamic methods. For example, it hasbeen noted that a value of m_(i)=0.0643 cm/s, which may be obtained bysonication in a system comprising a combination of an ultrasound sourceand an electrode system, could only be achieved by laminar flow in arotating disk electrode at a rotation speed of greater than 160,000 rpm,a value that is not practically attainable.

The second advantage of the sonoelectrochemical system is that theprocess of acoustic cavitation, namely the violent expansion andcollapse of gas bubbles within one acoustic cycle, can clean theelectrode surface and prevent passivation. The cleaning and erosion ofsolid surfaces by high power ultrasound is often termed cavitationalerosion. The prevention or reduction of electrode fouling by the use ofhigh power ultrasound has enabled electrochemical measurements to beapplied to the analysis of a wide range of complex samples that wouldotherwise require extensive sample preparation prior to the analysis.Sonoelectrochemical measurements have been applied to a number ofcomplex and potentially fouling systems, including manganese in tea,copper in whole blood, copper in beer, lead in human saliva, nitrite ineggs and the detection of lead in water following extraction into anorganic phase.

A critical aspect of sonoelectrochemical measurements is the relativepositioning of the acoustic horn that generates the high powerultrasound and the working electrode. In general, up until now, thecommonest configuration has been to position the acoustic generator andthe working electrode face on with a separation of typically 1-30 mm.This configuration is cumbersome and small variations in the relativepositioning of the acoustic generator and working electrode can lead tovariations of up to factors of 15 in the measured currents.Consequently, the accurate positioning of the acoustic generatorrelative to the working electrode is essential for the determination oflimiting currents.

In a high power acoustic resonator, an acoustic horn may be used togenerate high power ultrasound. The high power acoustic resonator maycomprise an acoustic or ultrasonic (the words may be usedinterchangeably herein) body, which may be referred to as an acoustichorn, which is a mechanical device for amplifying the displacement andmeans of generating a sinusoidal displacement—such as a piezoelectric ormagnetostrictive element. The displacement is generated by severalpiezoelectric elements and the amplification of the displacement isachieved by the reduction in cross-sectional area along the length ofthe horn, which is typically made of a metal such as steel or titanium.

FIG. 1 shows a schematic of a high power acoustic resonator that may beused in an embodiment of the present invention. Generally, a high poweracoustic resonator 10 may comprise an acoustic body/acoustic horn 15(the terms acoustic body and acoustic horn may be used interchangeablyherein) attached to and/or incorporating an ultrasonic transducer 20. Incertain aspects, the ultrasonic transducer 20 may be disposed within orcoupled to a base 25 of the acoustic horn 15. A power source 19 may becoupled with the ultrasonic transducer 20 to provide power to theultrasonic transducer 20. In an embodiment of the present invention, ahigh power acoustic resonator with integrated electrode system mayconsist of an ultrasonic piezoelectric transducer coupled to a suitablemetal horn.

In one aspect of such an embodiment, the piezoelectric transducer may beconfigured to operate in a longitudinal mode. In such an aspect, theresulting ultrasonic device may be characterized by having a sharpresonant frequency, which can be conveniently determined by themeasurement of the admittance (or impedance) spectrum of the device.Furthermore, the resonance frequency of the appropriate longitudinalmode of such a device is sensitive to any solid deposit that forms onthe tip of the horn and the magnitude of the frequency shift is ameasure of the mass loading. The high power acoustic resonator 10 maycomprise an ultrasonic piezoelectric transducer coupled to a suitablemetal horn and may operate in the frequency range 10-250 kHz and maydeliver high levels of acoustic power, typically in the range 1-500 W,when driven by a high input alternating voltage at its resonantfrequency.

The acoustic horn may oscillate laterally or may be configured tooscillate in a longitudinal mode. The resonant frequency of the acousticdevice operating in a longitudinal mode is determined by the thicknessof the piezoelectric, the acoustic horn 15 and the materials from whichthe piezoelectric and acoustic horn 15 are constructed. The acoustichorn 15 may have a stepwise tapering design, an exponentially reducingdiameter or the like. The acoustic horn 15 may be made of titanium andhave a sharp resonant frequency in air of 40 kHz, where the area of thehorn tip is of the order 0.2 cm². In some acoustic horn 15 designs, thetapering is degenerated to a single step giving the acoustic horn 15 apin-like shape. Other horn shapes can be envisaged, including the casewhere its thickness is very much less than the wavelength of sound andthe horn is a thin layer of material, for example but not by way oflimitation, that couples the ultrasonic transducer to the boreholefluids and their deposits.

Acoustic horns are devices for generating high power ultrasound. Anacoustic (or ultrasonic) horn may consist of a means of generating asinusoidal displacement, such as a piezoelectric or magnetostrictiveelement, and a mechanical device for amplifying the displacement. Thedisplacement of the acoustic horn may be generated by severalpiezoelectric elements and the amplification of the displacement isachieved by the reduction in cross-sectional area along the length ofthe horn, which is typically made of a metal such as steel or titanium.The horn is designed such that an anti-node is located at the tip of thehorn where the displacement is a maximum. When ultrasonic horns areoperated at high power levels, typically in excess of 10 W, theamplitude of the displacement of the tip may be several tens of microns.Operation of the ultrasonic horn at high power when the tip of the hornis immersed in liquids at ambient pressure will give rise to acousticcavitation in the liquid and the flow of liquid away from the tip by aphenomenon known as acoustic streaming. Acoustic cavitation in water atambient pressure is achieved at a power density in excess of 0.5-1.0 Wper square centimeter of horn tip and at a frequency of 20 kHz. In someembodiments of the present invention, the acoustic horn 15 may comprisea base end 25 that may provide a contact with the ultrasonic transducer20 to provide for the ultrasonic transducer 20 to vibrate the acoustichorn 15.

The resonant frequency of the acoustic device operating in alongitudinal mode may be determined by the size of the ultrasonictransducer 20 and the acoustic horn 15 and the materials from which theultrasonic transducer 20 and the acoustic horn 15 are constructed. Thedesign of the acoustic horn 15 may vary and may be a stepwise tapering,a smooth tapering with an exponentially reducing diameter or the like.The acoustic horn 15 may be designed such that the tapering isdegenerated to a single step giving the acoustic horn 15 a pin-likeshape. Other horn shapes can be envisaged, including the case where itsthickness is very much less than the wavelength of sound and the horn isa thin layer of material that is coupled to the ultrasonic transducer20. In embodiments of the present invention, the design of the acoustichorn 15 may be such as to amplify the acoustic energy onto the tip ofthe horn 17. In certain aspects of the present invention, the acoustichorn 15 may be made of titanium. Additionally, in certain aspects, thearea of the horn tip 17 may be of the order of 0.2-2.0 cm². In someembodiments of the present invention, the length of the acoustic horn 15is an odd integer multiple N of half the wavelength (λ/2) of theacoustic wave generated by the ultrasonic transducer 20.

FIG. 2 is a schematic-type diagram illustrating a high power acousticresonator with an integrated electrically conducting diamond electrode,in accordance with an embodiment of the present invention. In thedepicted embodiment, a high power acoustic resonator with an integratedelectrically conducting diamond electrode 50 is illustrated. The highpower acoustic resonator with an integrated electrically conductingdiamond electrode 50 may comprise an acoustic horn 15, a base 60 and atransducer 65. In certain aspects, the transducer 65 may be integratedinto the base 60 and in other aspects; the transducer 65 may be coupledwith the base 60.

In an embodiment of the present invention, the high power acousticresonator with an integrated electrically conducting diamond electrode50 may comprise an electrically conducting diamond electrode 70 disposedat a tip 17 of the acoustic horn 15. In certain aspects, the singleelectrically conducting diamond electrode 70 may comprise boron-dopeddiamond. In the illustrated embodiment, the electrically conductingdiamond electrode 70 may be electrically isolated from the acoustic horn15 by an isolating element 73. In certain aspects, the isolating element73 may comprise non-conducting diamond.

In an embodiment of the present invention, a diamond substrate may belocated at the tip 17 of the acoustic horn 15, wherein the diamondsubstrate may be of the order of about 1-10 millimeters in diameter andcomprise a ring of electrically non-conducting diamond with a centraldisc approximately 0.5-5.0 millimeters wide of boron-doped diamond. Thisdiamond substrate may be formed by taking a diamond substrate and dopinga central region with boron.

The conductive diamond in the diamond substrate may be fabricated by anymethod known to the art, but is preferably fabricated by doping duringgrowths and more preferably by doping with boron during growth. Analternative method of creating the conductive diamond region or regionsis to use ion implantation. Alternative dopants may include othersubstances capable of making the diamond substrate electricallyconductive.

An electrically conducting element 75, such as a copper or a silver wiremay be coupled with the electrically conducting diamond electrode 70. Inalternative embodiments, the electrically conducting element 75 maycomprise an electrically conducting channel or the like. In certainaspects, the electrically conducting element 75 may be brazed to theback of the electrically conducting diamond electrode using, forexample, a copper/silver/titanium active braze (e.g., EL-91 braze, madeby Drijfhout BV), which consists of a eutectic copper/silver wire (72weight percent silver) with a titanium core that constitutesapproximately 10 weight percent of the wire.

Merely by way of example, to provide for soldering/brazing using anon-active solder/braze of the electrically conducting element 75 to theelectrically conducting diamond electrode 70, the back of theelectrically conducting diamond electrode 70 may be coated with amixture of elements such that they bond to diamond and yield asolderable/brazeable surface. Merely by way of example, a method usingradio-frequency (“RF”) bias sputtering may be employed to sputtersequentially titanium, platinum and gold layers (approximately 0.1, 0.2and 1.0 μm in thickness, respectively) onto the back of the electricallyconducting diamond electrode 70 using a mechanical masking technique.The edge and rim of the isolating element 73 may also be coated with thesame titanium, platinum and gold layers by modifying the mechanical maskto facilitate the mounting of the diamond electrode into the recess inthe tip of the acoustic horn 17, noting that the geometries of the twometal layers must not generate any electrical contact between theultrasonic horn body 15 and the electrically conducting element 75either after sputter coating or after bonding the isolating element 73into the ultrasonic horn body 15. The tip of the ultrasonic horn 17 mayalso be coated with the same titanium, platinum and gold layers tofacilitate the brazing/soldering of isolating element 73.

In some methods of constructing the sonoelectrochemical probe, theelectrically conducting diamond electrode 70 and/or the isolatingelement 73 may be soldered into a recess that may be created/machinedinto the tip of acoustic horn 17. In such construction methods, thesolder used may have a lower melting point than the braze used to attachelectrically conducting element 75 to the electrically conductingdiamond electrode 70. Merely by way of example, such braze may comprisethe gold-germanium eutectic, which consists of gold and germanium in themole fraction ratio of 0.88:0.12 and has a melting point of around 365degrees Centigrade. Care must be taken during such soldering to ensurethat there is no electrical short circuit created between theelectrically conducting diamond electrode and the acoustic horn 15. Theelectrically conducting element 75 may be insulated from the acoustichorn 15 by surrounding the electrically conducting element 75 withnon-conducting tubing.

In one embodiment of the present invention, a central bolt 77 may bedisposed in or coupled with the base 60. The central bolt 77 may act toprovide access into an interior volume of the acoustic horn 15, provideaccess to the back of the electrically conducting diamond electrode 70,provide an anchoring point for the high power acoustic resonator with anintegrated electrically conducting diamond electrode 70, providestability for the high power acoustic resonator with an integratedelectrically conducting diamond electrode 70, and/or the like. Incertain aspects, the electrically conducting element 75 may be broughtto the interior/back of the acoustic horn 15 through a hole in thecentral bolt 77. Further, such integration in these embodiments mayprovide for a self-contained high power acoustic resonator with theintegrated electrically conducting diamond electrode that may besuitable for use in harsh conditions and/or for remote operations.

An alternative electrical connection to the electrically conductingdiamond electrode 70 may be made using wire bonding, which is atechnique much used in the integrated circuits industry. Implementationof the wire bonding technique may require the backside (the side thatmay be accessed from the interior of the acoustic horn 15) of theelectrically conducting diamond electrode 70 to be coated with a mixtureof elements chosen such that they bond to diamond and give awire-bondable surface. One such combination of elements, for example, isachieved by layers of titanium, platinum and gold (0.1, 0.2 and 1.0 μmin thickness, respectively), which may be applied by sequential RF biassputtering using photolithographical techniques. Again, care must betaken that the pattern coating is such a size and shape that there is noelectrical short circuit between the electrically conducting diamondelectrode 70 and the acoustic horn 15 either before or after bonding theisolating element 73 into the ultrasonic horn body 15.

FIG. 3 is a schematic-type diagram illustrating a high power acousticresonator with an integrated diamond electrode comprising a plurality ofconducting regions separated by non-conducting regions that may be usedas reference and/or counter and working electrodes, in accordance withan embodiment of the present invention. In certain embodiments of thepresent invention, the conducting-diamond electrode may comprise aplurality of electrically conducting diamond electrodes, illustrated inFIG. 3 as the electrically conducting diamond electrodes 101 a, 101 band 101 c, disposed in the tip 17 of the acoustic horn 15 with at leastone of the electrically conducting diamond electrodes 101 a, 101 b and101 c being electrically isolated from the acoustic horn 15. In suchembodiments, one or more of the electrically conducting diamondelectrodes 101 a, 101 b and 101 c may comprise boron-doped diamond. Incertain aspects, the acoustic horn 15 may comprise titanium.

In one embodiments of the present invention, the electrically conductingdiamond electrodes 101 a, 101 b and 101 c may be arranged such that theelectrically conducting diamond electrodes 101 a, 101 b and 101 c andthe tip 17 of the acoustic horn 15 are coplanar. In an alternativeembodiment, the electrically conducting diamond electrodes 101 a, 101 band 101 c may be disposed proximal to the tip 17. Such precisepositioning of the electrically conducting diamond electrodes 101 a, 101b and 101 c relative to the tip illustrates one of the advantages ofincorporating the conductive elements and other interfaces between theelectrically conducting diamond electrodes 101 a, 101 b and 101 c andelements external to the sonoelectrochemical probe within the acoustichorn.

In the illustrated embodiment, the electrically conducting diamondelectrode 101 a may comprise a disc surrounded by an electricallyinsulating region 105 a and 105 b, where insulating regions 105 a and105 b may comprise a single ring of non-conducting material surroundingthe electrically conducting diamond electrode 101 a. Similarly,electrically conducting diamond electrodes 101 b and 101 c may comprisea single ring of electrically conducting diamond and electricallyinsulating regions 105 c and 105 d may comprise a single ring ofelectrically insulating material. In certain aspects, the electricallyconducting diamond electrodes 101 a, 101 b and 101 c may compriseboron-doped diamond and the electrically insulating regions 105 a, 105b, 105 c and 105 d may comprise undoped diamond. In a furtherembodiment, the number of electrically conducting diamond andelectrically insulating diamond rings may be increased so long as thelast diamond ring is electrically insulating.

Merely by way of example, in a sonoelectrochemical probe in accordancewith one embodiment of the present invention, a diamond substrate may belocated at the tip 17 and this substrate may have a diameter ofapproximately 9 mm. This substrate may comprise a 2 mm diameter centralelectrically conducting diamond electrode, which may be used as aworking electrode, and may be surrounded by concentric rings ofelectrically non-conducting diamond alternating with concentric rings ofelectrically conducting diamond. Since diamond is itself anon-conducting substance, the concentric rings of electricallynon-conducting diamond may comprise diamond. The electrically conductingdiamond rings may comprise doped diamond where the dopant may be boron,phosphorus, sulfur or the like, or any other dopant providing forelectrical conduction by the doped diamond. The concentric rings of theelectrically conducting diamond may have widths of the order of about1-2 millimeters and, the concentric rings of the electricallynon-conducting diamond may have widths of the order of 1-2 millimeters.In certain aspects, one of the concentric rings of the electricallyconducting diamond, which is electrically insulated by the surroundingrings of non-conducting diamond, may function as a counter electrode ora reference electrode in an electrochemical circuit. In further aspectsanother electrically conducting diamond ring, which is electricallyinsulated by the surrounding rings of electrically non-conductingdiamond, may function as another reference electrode or counterelectrode.

In an embodiment of the present invention, electrical contact with oneor more of the electrically conducting diamond electrodes 101 a, 101 band 101 c may be made using electrically-conducting channels 117 thatare located in an insulating channel-support-matrix 115. In certainaspects, the electrically conducting channels 117 and the insulatingchannel-support-matrix 115 may comprise a drilled, solder-filled PCBboard or a laser drilled electrically non-conducting diamond platefilled with an active metal braze. Merely by way of example, theelectrically-conducting channels 117 may have diameters of the order offractions of millimeters and the electrically-conducting channels 117may comprise channels in the insulating channel-support-matrix 115 thatmay be filled with a mixture of copper, silver and titanium braze or thelike. The electrically conducting channels 117 may be positioned suchthat one or more of the electrically conducting channels 117 is incontact with one of the electrically conducting diamond electrodes 101a, 101 b or 101 c.

A plate may be used to help position and/or provide structural supportto the insulating channel-support-matrix 115 and diamond electrode. Incertain aspects, the plate 120 may comprise ceramic, plastic or thelike. The insulating channel-support-matrix 115 and the electricallyconducting channels 117 may be held in contact with the underside of theelectrode array, where the electrode array comprises the electricallyconducting diamond electrodes 101 a, 101 b or 101 c and the electricallyinsulating regions 105 a, 105 b, 105 c and 105 d, by a mechanicalsupport 120. The mechanical support 120 may include one or more holesthrough which electrically conducting elements or channels 110 a and 110b may pass and make contact with the electrically conducting channels117. The electrically conducting elements or channels 110 a and 110 bmust not make electrical contact with the mechanical support 120 shouldthe mechanical support 120 be made of an electrically conductingmaterial such as a metal.

In certain aspects, the electrically conducting element s or channels110 a and 110 b may be soldered or wire bonded to the electricallyconducting diamond electrodes 101 a, 101 b or 101 c. Further, in certainaspects, electrically conducting elements or channels 110 a and 110 bmay pass through and out of the acoustic horn 15 through a hole in thecentral bolt 77 or the like. The electrically conducting elements orchannels 110 a and 110 b may be connected to electrical sources,processors and/or the like to provide for operation and or analysis ofone or more of the electrically conducting diamond electrodes 101 a, 101b or 101 c. In one embodiment of the present invention, the insulatingchannel-support-matrix 115 and the mechanical support 120 may bemachined to provide that the insulating channel-support-matrix 115 andthe mechanical support 120 key mechanically into each other. In thisway, the orientation of the electrically conducting channels 117 and theone or more holes in the mechanical support 120 may be maintained duringassembly.

In one embodiment of the present invention, a top surface of theinsulating channel-support-matrix 115 may be patterned with a metallayer to provide for electrical contact to the underside of the one ormore electrically conducting diamond electrodes 101 a, 101 b or 101 c,such metal layer may comprise: (a) a standard copper layer, such as isused on a PCB board, and may be applied to the insulatingchannel-support-matrix 115 using standard PCB patterning and etchtechniques; (b) sequential layers of titanium, platinum and gold andthese layers may be applied to the insulating channel-support-matrix 115by RF bias sputtering using a mechanical or photolithographical mask.Further, in some embodiments of the present invention, the bottomsurfaces of the electrically conducting diamond electrodes 101 a, 101 bor 101 c may be sequentially RF bias sputtered with titanium, platinumand gold layers using a mechanical or lithographic mask to provide thatthe pattern produced by the sputtering matches the metal layer patternon the insulating channel-support-matrix 115.

In certain fabrication methods, the acoustic horn 15 may comprise twoparts to allow for the electrode system to be assembled and the twoparts may be affixed together after the electrode system has been beassembled. Affixation of the two parts may be provided by screws, bolts,gluing, soldering, welding and/or the like.

In certain embodiments of the present invention, the one or more of theelectrically conducting diamond electrodes 101 a, 101 b or 101 cprovided as a counter electrode may be configured in the electricalarrangement to act as a second working electrode. In such embodiments,an external counter may be utilized with the sonoelectrochemical probe.Such configurations may provide for obtaining information about eitherthe electrochemical processes occurring at the working electrode(s)and/or the flow of species across the electrically conducting diamondelectrodes 101 a, 101 b or 101 c.

FIG. 4 is a schematic-type diagram illustrating a high power acousticresonator with an integrated diamond electrode array, in accordance withan embodiment of the present invention. In certain aspects, theillustrated sonoelectrochemical probe 150 comprises a diamond electrodearray 155. The diamond electrode array 155 may comprise a substrateacross which may be an array of conducting and non-conducting regions.In one aspect of the present invention, the substrate may comprisediamond, the conducting regions may comprise doped diamond regions andthe non-conducting regions may comprise diamond. In such embodiments,the doped diamond regions may be doped with a dopant such as boron,phosphorous, sulfur, arsenic or the like. The diamond electrode array155 may be a macro-array and/or a micro-array.

Similar to the embodiment described in FIG. 3, the diamond electrodearray 155 may be supported by a non-conducting support layer (not shown)through which conducting channels and/or elements may provide electricalcontact with the conducting regions of the diamond electrode array 155.In some aspects of the present invention, a sapphire ring 165 may bebrazed into a recess in the acoustic horn 15 using techniques that maybe appreciated by those of skilled in the art. In such aspects, aportion of a top surface of the sapphire ring 165 and a bottom surfaceof the diamond electrode array 155 may both be coated with a mixture ofelements such that they bond to diamond and sapphire and yield brazeablesurfaces. This brazeable surface may comprise sequential metal layers oftitanium, platinum and gold that may be generated using an RF biassputtering technique with a mechanical mask or the like. In anembodiment of the present invention, the diamond electrode array 155 maybe soldered onto the top surface of the sapphire ring 165. In certainaspects, the solder used to solder the diamond electrode array 155 tothe top surface of the sapphire ring 165 may have a lower melting pointthan a braze, solder or the like used to solder/braze the sapphire ring165 to the acoustic horn 155.

In embodiments in which the diamond electrode array 155 is soldered tothe sapphire ring, the soldering may require careful positioning of thediamond electrode array 155 to provide that an electrical short circuitis not created between one or more of the conducting regions of thediamond electrode array 155 and the acoustic horn 15. In certainembodiments, a non-conducting adhesive 170 may be disposed at a gapbetween the diamond electrode array 155 and the acoustic horn 15. Thenon-conducting adhesive 170 may be a liquid non-conducting glue, such asEPO-TEC 353ND epoxy, or the like. In certain fabrication methods forsome embodiments of the present invention, vacuum outgassing may be usedto provide for good penetration of the non-conducting adhesive 170 intothe gap prior to hardening.

In one embodiment of the present invention, electrical contact with thediamond electrode array 155 may be made using a conductive element 185.In certain aspects, the conductive element 185 may be a gold-plated pinor the like. The conductive element 185 may be disposed to provide forcontact with a rear-surface of the diamond electrode array 155. Incertain embodiments of the present invention, one or more non-conductingplastic members 180 a and 180 b may be used keep an end of theconductive element 185 in contact with the rear-surface of the diamondelectrode array 155. In one embodiment, a spring 160 may be used inconjunction with the one or more non-conducting plastic members 180 aand 180 b to provide for keeping the conductive element 185 in contactwith the rear-surface of the diamond electrode array 155. In certainaspects, the one or more non-conducting plastic members 180 a and 180 bmay be disposed throughout the entire length of the inside of theacoustic horn 15 and electrically conducting wires, electricallyconducting channels and/or the like may be disposed within the one ormore non-conducting plastic members 180 a and 180 b to provide that anelectrical short circuit does not occur.

In certain embodiments, as described in more detail with reference toFIG. 3, the conductive element 185 may comprise one or more electricallyconducting elements or channels, an insulating channel-support-matrix, amechanical support and/or the like and may be connected to a pluralityof conducting wires of the like to provide for selective electricalsupply to and/or selective processing of one or more of the conductiveregions of the diamond electrode array 155.

In the foregoing description, for the purposes of illustration, variousmethods and/or procedures were described in a particular order. Itshould be appreciated that in alternate embodiments, the methods and/orprocedures may be performed in an order different than that described.It should also be appreciated that the methods described above may beperformed by hardware components and/or may be embodied in sequences ofmachine-executable instructions, which may be used to cause a machine,such as a general-purpose or special-purpose processor or logic circuitsprogrammed with the instructions, to perform the methods.

Hence, while detailed descriptions of one or more embodiments of theinvention have been given above, various alternatives, modifications,and equivalents will be apparent to those skilled in the art withoutvarying the invention. Moreover, except where clearly inappropriate orotherwise expressly noted, it should be assumed that the features,devices and/or components of different embodiments may be substitutedand/or combined. Thus, the above description should not be taken aslimiting the scope of the invention, which is defined by the appendedclaims.

What is claimed is:
 1. An erosion and wear resistant sonoelectrochemicalprobe, comprising: an acoustic resonator, wherein the acoustic resonatorcomprises: an acoustic body comprising a base and a tip having an area;a transducer coupled with the base and configured to vibrate theacoustic body; a working electrode coupled with the tip of the acousticbody and disposed within the area of the tip at or proximal to a planedefined by the tip of the acoustic body, wherein the working electrodecomprises boron-doped diamond; a reference electrode also coupled withthe tip of the acoustic body and disposed within the area of the tip ata plane defined by the tip of the acoustic body, wherein the referenceelectrode comprises boron-doped diamond; and electrically conductingelements coupled with the working and reference electrodes, wherein theelectrically conducting elements are electrically insulated from theacoustic body and each other.
 2. The sonoelectrochemical probe of claim1, wherein the electrically conducting elements are disposed within theacoustic body passing from the tip to the base and there-through to anelectrical source.
 3. The sonoelectrochemical probe of claim 1, furthercomprising: a counter electrode coupled with the tip of the acousticbody and also disposed within the area of the tip at a plane defined bythe tip of the acoustic body.
 4. The sonoelectrochemical probe of claim1, wherein the acoustic body comprises an acoustic horn.
 5. Thesonoelectrochemical probe of claim 4, wherein a fundamental resonantfrequency of said acoustic horn is in the frequency range of 10-250 kHz.6. The sonoelectrochemical probe of claim 1, wherein the transducer isconfigured to vibrate the acoustic body in a longitudinal mode.
 7. Anerosion and wear resistant sonoelectrochemical probe, comprising: anacoustic resonator, wherein the acoustic resonator comprises: anacoustic body comprising a base and a tip having an area; a transducercoupled with the base and configured to vibrate the acoustic body; adiamond electrode coupled with the tip of the acoustic body and disposedwithin the area of the tip at a plane defined by the tip of the acousticbody, wherein the diamond electrode comprises a working electrode and areference electrode, the working electrode and the reference electrodeeach comprising boron-doped diamond; and electrically conductingelements coupled with the working and reference electrodes, wherein theelectrically conducting elements are electrically insulated from theacoustic body and each other.
 8. The sonoelectrochemical probe of claim7, wherein the diamond electrode comprises diamond doped with an n-typeor p-type dopant.
 9. The sonoelectrochemical probe of claim 7, whereinthe diamond electrode comprises a central disc of boron-doped diamondsurrounded by a concentric ring of non-conducting diamond, and whereinthe concentric ring of electrically non-conducting diamond provides forthe insulation of the central disc of the boron-doped diamond from theacoustic body.
 10. The sonoelectrochemical probe of claim 7, wherein theelectrically non-conducting diamond comprises intrinsic diamond.
 11. Thesonoelectrochemical probe of claim 7, wherein the diamond electrodecomprises an array of electrically conducting diamond regions andelectrically non-conducting diamond regions.
 12. The sonoelectrochemicalprobe of claim 11, wherein: the electrically conducting diamond regionscomprise boron-doped diamond; and the electrically non-conductingdiamond regions comprise intrinsic diamond.
 13. The sonoelectrochemicalprobe of claim 11, wherein the array of electrically conducting diamondregions and electrically non-conducting diamond regions is configured ina diamond substrate.
 14. The sonoelectrochemical probe of claim 11,wherein the working electrode comprises at least one of the electricallyconducting diamond regions.
 15. The sonoelectrochemical probe of claim11, wherein the reference electrode comprises at least one of theelectrically conducting diamond regions.
 16. An erosion and wearresistant sonoelectrochemical probe, comprising: an acoustic resonator,wherein the acoustic resonator comprises: an acoustic body comprising abase and a tip having an area; a transducer coupled with the base andconfigured to vibrate the acoustic body; a diamond electrode coupledwith the tip of the acoustic body and disposed within the area of thetip, wherein the diamond electrode comprises a working electrode and areference electrode; and one or more electrically conducting elementscoupled with the working and reference electrodes, wherein the one ormore electrically conducting elements are electrically insulated fromthe acoustic body and, if more than one, from each other; wherein one ormore of the working electrode and the reference electrode form one ormore electrically conducting portions of an array of electricallyconducting diamond regions and electrically non-conducting diamondregions; wherein the array comprises a central disc of boron-dopeddiamond, a first plurality of concentric rings of electricallynon-conducting diamond, and a second concentric ring or plurality ofconcentric rings of boron-doped diamond; wherein the first plurality ofconcentric rings of the electrically non-conducting diamond and thesecond concentric ring or plurality of concentric rings of theboron-doped diamond are arranged alternately around the central disc ofboron-doped diamond; and wherein the central disc of boron-doped diamondand the second concentric rings or plurality of concentric rings of theboron-doped diamond each are coupled with at least one of the one ormore electrically conducting elements.
 17. The sonoelectrochemical probeof claim 16, wherein the working electrode comprises at least one of thecentral disc of boron-doped diamond and the second concentric ring orplurality of concentric rings of boron-doped diamond.
 18. A method ofobtaining electrochemical measurements from a substance in a liquid, themethod comprising: using the sonoelectrochemical probe of claim 1 withthe tip immersed in the liquid; and obtaining electrochemicalmeasurements using the sonoelectrochemical probe, wherein the acousticresonator is operated with sufficient power to cause acoustic cavitationin the liquid and clean the reference and working electrodes.